46 



DISCOVERY REPORTS 



Table 8 



* Excluding uncountable colonies. f Excluding gelatinous colonies. 



From the above table it will be seen that at the two inshore stations the dominant 

 forms were Chaetoceros socialis, Ch. neglechis and Thalassiosira a?itarctica, with lesser 

 numbers of Eiicampia antarctica and Fragilaria antarctica. It will be seen that besides 

 the normal chain form that can be readily estimated, large numbers of minute gelatinous 

 colonies of Thalassiosira were present, as indicated by the asterisk after the estimated 

 numbers. It is at these two stations that the influence of the western Weddell Sea 

 water is most strongly exhibited. In all the material examined for this report Chaetoceros 

 socialis has only twice been recorded in any other type of surface water. The pronounced 

 dominance of Thalassiosira antarctica over the other countable forms may also be taken 

 as typical of western Weddell Sea conditions, as this species, though undoubtedly a 

 spring form, was still numerous in water of this type near Joinville Island later in the 

 season, whereas at the stations worked towards the Bellingshausen Sea it never reached 

 anything like the same prominence. 



At the four outer stations on the Annekov Island line it will be seen that the general 

 character of the phytoplankton remained very much the same throughout. Chaetoceros 

 socialis did not occur, and it will be noted later on how extremely sporadic is the dis- 

 tribution of this form. The dominant forms were Fragilaria antarctica, Thalassiosira and 

 Chaetoceros criophilum and lesser numbers of Thalassiothrix antarctica and Nitzschia 

 seriata, indicative of slight admixture with Bellingshausen Sea water. It will be noted 

 that the percentage of Fragilaria increased steadily towards the south-west ; pack-ice 

 was present in that direction at the time, and as will be noted on many subsequent 

 occasions, the abundant occurrence of this species in the plankton at any distance from 

 land appears to be closely correlated with the presence of melting pack-ice. The probable 

 significance of this is discussed later. 



Heavy hauls containing large numbers of species, with small colonial forms dominant. 



